Generally, a dye-sensitized solar cell is a solar cell chemically generating power using the solar light absorption ability of a dye, and, as shown in FIG. 1, includes an anode 103, a dye, an electrolyte 105, a counter electrode 104, a conductive transparent electrode 102 and a sealing adhesive 106 between lower and upper glass substrates 101.
The anode 103 is made of an N-type oxide semiconductor, such as TiO2, ZnO, SnO2 or the like, having a wide bandgap and existing in the form of a nanoporous film, and is adsorbed on the surface thereof with a monomolecular layered dye. When solar light is incident on a solar cell, Fermi energy-leveled electrons in the dye absorb solar energy to be excited to a higher energy level at which electrons are not fully filled.
In this case, the vacant site at a low energy level, from which electrons have left, is refilled with electrons received from ions in an electrolyte. The ions having provided electrons to a dye move to a counter electrode 104 and receive electrons therefrom. In this case, the counter electrode 104, which is a cathode, serves to provide electrons to ions in an electrolyte through an oxidation-reaction reaction occurring on the surface thereof because it acts as a catalyst for the oxidation-reduction reaction of ions in the electrolyte.
Among the constituents of the dye-sensitized solar cell, each of the upper and lower glass substrates 101 is coated with a conductive transparent electrode 102. The conductive transparent electrode 102 is generally made of a fluorine-doped tin oxide (FTO). The reason for this is that the FTO can be stably used for a long time because the reactivity of the FTO with the electrolyte 105 is lowest.
Further, in order to prevent the electrolyte 105 from leaking out of the solar cell, the solar cell is structured such that the conductive transparent electrode 102 is enclosed using a sealing adhesive 106, thus accommodating the electrolyte 105 in a predetermined space.
However, since the upper and lower glass substrates, each of which is coated with FTO, are very expensive, there is a problem in that the price of the dye-sensitized solar cell increases, and thus it is difficult to commercialize the dye-sensitized solar cell.
Further, there is a problem in that the sealing performance of the sealing adhesive 106 is deteriorated by the pressure asymmetrically applied to the dye-sensitized solar cell to form minute gaps, so the electrolyte 106 in the dye-sensitized solar cell is discharged to the outside through the gaps, and moisture is externally introduced into the dye-sensitized solar cell, thereby decreasing the efficiency of the dye-sensitized solar cell.
Meanwhile, since the conductive transparent electrode 102, the sealing adhesive 106 and the lower and upper glass substrates 101 are different from one another in thermal expansion coefficient and thermal conductivity, they easily break or are not easily sealed in a small temperature difference, so the electrolyte in the dye-sensitized solar cell leaks out of the cell, thereby decreasing the efficiency of the dye-sensitized solar cell.